Whitefly in greenhouse

Greetings
Any ideas or solutions to the following problem?
I am growing potato plants in a greenhouse which becomes infected with
whitefly when the weather gets warm. In the past I have used various
pesticides to control the problem to a certain degree. However, I am now
starting a series of eperiments in which the plants will be drought
stressed and would like to avoid spraying them. Does anyone know of a
plant that could be grown alongside the potatoes to ward off the
whitefly? (It has been reported that some plants will keep aphids at
bay). BTW, I have tried "fogging" the greenhouse with fumigation tablets
that one sets alight but with little success.
All comments welcome
Dieter Kieck
Genetics Department
Wits University
Johannesburg
South Africa